The present invention relates to a method for manufacturing a microlens substrate, and to a microlens substrate, an opposing substrate for a liquid crystal panel, a liquid crystal panel, and a projection display apparatus.
Hitherto, a projection display apparatus for projecting images on a screen has been known. In a projection display apparatus of this type, liquid crystal panels (liquid crystal optical shutters) are generally used for forming images.
The liquid crystal panel includes, for example, a liquid crystal driving substrate for driving liquid crystals and an opposing substrate for a liquid crystal panel bonded to each other via a liquid crystal layer. Some liquid crystal panels are provided with a number of minute microlenses in positions, each corresponding to a pixel of the opposing substrates for liquid crystal panels. Light transmitted by the opposing substrate for a liquid crystal panel is condensed by the microlenses, thereby improving the transmissivity of the light. The microlenses are generally formed on a microlens substrate provided in the liquid crystal panel.
A known microlens substrate includes a glass substrate provided with a number of concavities, a glass layer bonded to the glass substrate at a surface thereof provided with the concavities via a resin layer, and microlenses formed with a resin filling the concavities.
In order to obtain a maximum power of the microlenses, a resin having a highest possible index of refraction is used for forming the resin layer disposed between the glass substrate and the glass layer. The resin having a high index of refraction has relatively high viscosity before curing. Therefore, a problem occurs, as described below.
When the glass substrate and the glass layer are bonded to each other via the resin, non-uniformity in the thickness of the resin layer obtained by curing the resin is produced due to low fluidity of the resin because of the relatively high viscosity thereof. Due to low fluidity of the resin, air bubbles are difficult to remove in a bonding process, whereby there is a risk of the air bubbles remaining in the resin layer. Non-uniformity in the thickness of the resin layer and remaining air bubbles will deteriorate the optical characteristics.
Accordingly, an object of the present invention is to provide a method for manufacturing a microlens substrate, and to provide a microlens substrate, an opposing substrate for a liquid crystal panel provided with the microlens substrate, a liquid crystal panel, and a projection display apparatus, in which the thickness of a resin layer is made uniform, and air bubbles are prevented from remaining.
To the end, according to the present invention, a method for manufacturing a microlens substrate comprises the steps of preparing a glass substrate provided with a number of concavities formed on a surface thereof; supplying a resin having a viscosity before curing of not greater than 500 cP at a temperature of 25xc2x0 C. onto the surface of the glass substrate provided therein with the concavities; bonding a glass layer to the glass substrate via the resin; and forming microlenses in the concavities by curing the resin. An index of refraction n of the resin after curing is preferably not lower than 1.35. The resin may be an ultraviolet curable resin.
A microlens substrate according to the present invention, manufactured by the method according to the present invention, comprises a glass substrate provided with a number of concavities; a glass layer bonded to the glass substrate via a resin layer; and microlenses formed with a resin filling the concavities.
The resin layer is formed by curing a resin having a viscosity before curing of not higher than 500 cP at 25xc2x0 C.
An index of refraction n of the resin after curing is preferably not lower than 1.35. The resin may be an ultraviolet curable resin. The microlens substrate and a transparent conductive film provided on the glass layer or the glass substrate are preferably included. A liquid crystal panel may be configured with the microlens substrate, a black matrix provided on the glass layer or on the glass substrate, and a transparent conductive film covering the black matrix. The liquid crystal panel may include an opposing substrate for a liquid crystal panel.
A liquid crystal panel is enabled, which includes a liquid crystal driving substrate provided with a plurality of pixel electrodes, the opposing substrate for a liquid crystal panel bonded to the liquid crystal driving substrate, and liquid crystals sealed into a gap between the liquid crystal driving substrate and the opposing substrate for a liquid crystal panel. Preferably, the liquid crystal driving substrate is a TFT substrate. A projection display apparatus is enabled, which includes light valves having the liquid crystal panels, and projects images by using at least one of the light valves. The projection display apparatus is enabled, which includes three light valves corresponding to red, green, and blue, a light source, a color-splitting optical system for splitting light from the light source into red, green, and blue light beams and guiding the light beams to the corresponding light valves, a color-synthesizing optical system for synthesizing the images, and a projection display apparatus for projecting the synthesized images. In the projection display apparatus, the light valves include the liquid crystal panels.